The invention relates to neutron tubes or sources, and more particularly to neutron tubes or sources based on plasma ion generators, including compact neutron tubes or sources which generate a relatively high neutron flux using the D-D reaction.
Conventional neutron tubes employ a Penning ion source and a single gap extractor. The target is a deuterium or tritium chemical embedded in a molybdenum or tungsten substrate. Neutron yield is limited by the ion source performance and beam size. The production of neutrons is limited by the beam current and power deposition on the target. In the conventional neutron tube, the extraction aperture and the target are limited to small areas, and so is the neutron output flux.
Commercial neutron tubes have used the impact of deuterium on tritium (D-T) for neutron production. The deuterium-on-deuterium (D-D) reaction, with a cross section for production a hundred times lower, has not been able to provide the necessary neutron flux. It would be highly desirable and advantageous to make high flux D-D neutron sources feasible. This will greatly increase the lifetime of the neutron generator, which is unsatisfactory at present. For field applications, it would greatly reduce transport and operational safety concerns. For applications such as mine detection, where thermal neutrons are presently used, the use of the lower energy D-D neutrons (2.45 MeV rather than 14.1 MeV) also would decrease the size of the neutron moderator.
High brightness or point neutron sources, i.e. sources in which the neutrons appear to be coming from a point source, are needed in radiography applications. To make a bright neutron source, the target dimensions must be small and the ion current impinging on the target must be high. In conventional neutron generators, the ion source can produce only low current density with low atomic deuterium ion species. Also, since the target dimensions of conventional sources are large, the neutron beam must be collimated to project back to a point source area. Therefore, a neutron source based on D-D reactions which has a high ion current impinging on a small target would be highly advantageous.
Applications of a high brightness neutron source include neutron radiography; non-proliferation; mine detection; boron neutron capture therapy (BNCT); and material studies. A neutron generator design with a small target area and a high ion current incident on the target would be highly advantageous.